JP2005264114A - Method for producing rubber composition, rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a rubber composition in which a rubber gauge of an inner liner and a white side wall cover can thinly be retained without lowering the viscosity, and to provide a rubber composition obtained by the production method and a pneumatic tire in which the rubber composition is used for an inner liner or white side wall cover. <P>SOLUTION: The method for producing the rubber composition comprises dividedly kneading zinc oxide into a rubber component containing 35-85 wt.% halogenated rubber. In the production method, the rubber composition is composed of the rubber component and zinc oxide in a compounding amount of 2-8 pts. wt. based on 100 pts. wt. rubber component and 10-55 wt.% of total zinc oxide is kneaded and discharged at 130-160°C in a first kneading step. In the pneumatic tire, the rubber composition is used for the inner liner or white side wall cover rubber. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a rubber composition, a rubber composition, and a pneumatic tire.

  Conventionally, butyl rubber, which does not easily allow air to pass through, has been used for the inner liner of a tire. This makes it possible to reduce the thickness of the rubber gauge while maintaining internal pressure retention, thereby reducing the weight of the tire. In order to obtain co-curability with a carcass topping rubber, a blend of natural rubber with butyl rubber or a halogenated butyl rubber is also used.

  However, when a conventional rubber composition is used, the temperature of the rubber is lowered during vulcanization, so that the viscosity of the rubber decreases, and the cord enters the tire inner liner due to thermal contraction of the carcass cord. As a result, there is a problem that the rubber gauge from the lower end of the cross section of the carcass cord to the inner liner surface cannot be kept thin. For ordinary diene rubbers, in order to prevent intrusion of the cord, a method of making the rubber semi-vulcanized by irradiating it with an electron beam after rolling the rubber is often used. Since the system rubber has a property that the semi-vulcanized state cannot be obtained by electron beam irradiation and the viscosity is lowered, it is necessary to provide a certain rubber gauge before vulcanization, The weight of the tire could not be reduced.

  On the other hand, in a pneumatic tire having a white sidewall, it does not contain pollutant chemicals (aromatic oil, pollutant anti-aging agent, etc.) as black rubber (hereinafter referred to as white cover rubber) covering the white rubber. The white cover rubber applied before vulcanization completely covers the white rubber even after vulcanization, and sufficient ozone resistance when used for tires after vulcanization. And having resistance to bending crack growth. In order to satisfy these requirements, the white cover rubber originally contains butyl rubber with few double bonds, ethylene-propylene-diene rubber (EPDM) that does not have double bonds in the main chain, and polybutadiene rubber has been conventionally used. The method of blending has been performed.

  However, when a conventional rubber composition is used, the viscosity of the rubber decreases as the temperature rises during vulcanization, and the white rubber gauge is pressed against the uneven sidewall mold as it is. When the thickness is small, the inner white rubber is exposed. In addition, white rubber penetrated into the spew generated after vulcanization, and the white rubber was exposed after cutting the spew. In order to prevent such problems, the cover rubber must be provided with a gauge above a certain level before vulcanization, and the tire can be reduced in weight as with the rubber composition used for the inner liner. could not.

  In Patent Document 1, in the production of a carcass topping rubber, for example, by dividing and kneading zinc oxide into a rubber component containing a bromide of a p-methylstyrene-isobutylene copolymer, performance is maintained even during long-term storage. A rubber composition that is difficult to decrease is disclosed. However, since the blended amount of bromide in the rubber component is too small, there is a problem that when the tire is manufactured using the obtained rubber composition as an inner liner, the air permeation resistance is poor.

JP 2000-264010 A

  An object of the present invention is to provide a rubber composition that can keep a rubber gauge of an inner liner or a white cover thin in a tire manufacturing process without reducing the viscosity of the rubber even when a butyl rubber is used as a rubber component. It is an object to provide a production method, a rubber composition obtained by the production method, and a pneumatic tire using the rubber composition for an inner liner or a white cover rubber.

  The present invention is characterized in that zinc oxide is divided and kneaded into a rubber component containing 35 to 85% by weight of a halogenated butyl rubber and / or a halogenated copolymer of isobutylene and p-methylstyrene. In the method for producing a rubber composition, the rubber composition comprises a rubber component and zinc oxide in an amount of 2 to 8 parts by weight based on 100 parts by weight of the rubber component. The method for producing a rubber composition according to claim 1, wherein 10 to 55% by weight of zinc is kneaded and discharged at 130 to 160 ° C.

  The present invention relates to a rubber composition obtained by the production method.

  The present invention also relates to a pneumatic tire having an inner liner made of the rubber composition.

  Furthermore, the present invention relates to a pneumatic tire having a white side wall cover rubber made of the rubber composition.

  According to the present invention, a specific amount of halogenated butyl rubber is used as a rubber component, and zinc oxide is divided and kneaded to reduce the rubber gauge of the inner liner and the white cover in the tire manufacturing process without reducing the viscosity. It can hold | maintain and the further weight reduction of a tire is attained.

  The rubber composition of the present invention comprises a rubber component and zinc oxide.

  As the rubber component, a halogenated butyl rubber and / or a halide of a copolymer of isobutylene and p-methylstyrene is contained as an essential component.

  As the halogen type of the halogenated butyl rubber and / or the halide of the copolymer of isobutylene and p-methylstyrene, chlorine or bromine is preferable.

  The halogen content of the halide of the copolymer of halogenated butyl rubber and / or isobutylene and p-methylstyrene is preferably 1.1 to 2.2% by weight. When the halogen content is less than 1.1% by weight, the vulcanization rate is too slow, the co-vulcanizability with the adjacent rubber is poor, and the adhesive strength tends to decrease. On the other hand, if the halogen content exceeds 2.2% by weight, the vulcanization rate is too high and the steel tends to be scorched during processing.

  The content of the halogenated butyl rubber and / or the copolymer of isobutylene and p-methylstyrene in the rubber component is 35% by weight or more and 85% by weight or less.

  In particular, when the obtained rubber composition is used as an inner liner, the halide content of the halogenated butyl rubber and / or copolymer of isobutylene and p-methylstyrene is preferably 65% by weight or more. 70% by weight or more is more preferable. If it is less than 65% by weight, the air permeation resistance tends to be inferior. The halogenated butyl rubber and / or halide content of a copolymer of isobutylene and p-methylstyrene is preferably 85% by weight or less. If it exceeds 85% by weight, the co-curability with the adjacent rubber is poor, and the adhesive strength tends to decrease.

  When the obtained rubber composition is used as a white cover rubber, the halide content of the halogenated butyl rubber and / or copolymer of isobutylene and p-methylstyrene is 35% by weight or more, It is preferable that it is weight% or more. If the content is less than 35% by weight, there is a problem in compatibility with EPDM. Further, the halogenated butyl rubber and / or the halogenated product of the copolymer of isobutylene and p-methylstyrene is preferably 45% by weight or less, and more preferably 41% by weight or less. When it exceeds 45% by weight, the flex crack growth tends to be inferior.

  Rubber components other than halogenated butyl rubber, halogenated copolymer of isobutylene and p-methylstyrene include natural rubber, polybutadiene rubber, ethylene-propylene-diene rubber (EPDM), polyisoprene rubber, styrene-butadiene rubber, acrylonitrile. -Diene rubber such as butadiene rubber is used. Among these, it is preferable to use natural rubber from the viewpoint of co-vulcanizability with the adjacent rubber, and in the case of a rubber composition for an inner liner, the content of the natural rubber in the rubber component is preferably 15 to It is preferably 35% by weight. These rubbers may be used alone or in combination of two or more.

  The blending amount of zinc oxide in the present invention is preferably 2 parts by weight or more and 8 parts by weight or less with respect to 100 parts by weight of the rubber component.

  In particular, when the obtained rubber composition is used as an inner liner, the compounding amount of zinc oxide is preferably 3 parts by weight or more, more preferably 4 parts by weight or more with respect to 100 parts by weight of the rubber component. preferable. If the blending amount of zinc oxide is less than 3 parts by weight, it tends to be difficult to obtain an appropriate vulcanization rate. Moreover, it is preferable that the compounding quantity of a zinc oxide is 8 weight part or less, and it is more preferable that it is 6 weight part or less. If the blending amount of zinc oxide exceeds 8 parts by weight, the vulcanization speed is too fast and there is a tendency to cause scorch during processing.

  When the obtained rubber composition is used as a white cover rubber, the compounding amount of zinc oxide is preferably 2 parts by weight or more, and 2.5 parts by weight or more with respect to 100 parts by weight of the rubber component. It is more preferable. When the blending amount of zinc oxide is less than 2 parts by weight, it tends to be difficult to obtain a good vulcanization rate. Moreover, it is preferable that the compounding quantity of a zinc oxide is 4 weight part or less, and it is more preferable that it is 3.5 weight part or less. When the blending amount of zinc oxide exceeds 4 parts by weight, the vulcanization speed is too high and there is a tendency to cause scorch during processing.

  In the method for producing a rubber composition of the present invention, zinc oxide is divided and kneaded into the rubber components.

  In general, when kneading halogenated butyl rubber, zinc oxide is usually kneaded in the second step of kneading a vulcanizing agent in order to produce a carbon-carbon bond by dehalogenation. However, even if the entire amount of zinc oxide is kneaded in the second kneading step, the expected increase in viscosity does not occur. Further, when half of the total amount of zinc oxide is kneaded in the first kneading step, the vulcanization reaction proceeds too much, and there is a tendency that a decent rubber dough cannot be obtained. Therefore, in the present invention, zinc oxide is kneaded by being divided at a specific ratio into the first kneading step and the second kneading step. By using the rubber composition obtained by such a kneading method, the viscosity of the rubber does not decrease even if the prepared inner liner rubber gauge is reduced. It is possible to manufacture a tire with a thinner gauge and a lighter weight. Similarly, even if the white cover rubber gauge is reduced, exposure of white rubber, which is a problem in the tire manufacturing process, and intrusion into the spew are prevented, making it possible to manufacture a lightweight white sidewall tire. .

  The blending amount of zinc oxide in the first kneading step is preferably 10% by weight or more, more preferably 20% by weight or more of the total zinc oxide. If the blending amount of zinc oxide in the first kneading step is less than 10% by weight, the viscosity of the rubber kneaded tends to be too low to obtain a good rubber remaining gauge. The blending amount of zinc oxide in the first kneading step is preferably 55% by weight or less, more preferably 50% by weight or less, and particularly preferably 30% by weight or less of the total zinc oxide. When the blending amount of zinc oxide exceeds 55% by weight, the viscosity tends to increase too much during the kneading process, and a good rubber fabric tends not to be obtained.

  The discharge temperature in the first kneading step is preferably 130 ° C. or higher, more preferably 140 ° C. or higher. If the discharge temperature is less than 130 ° C., the expected increase in rubber viscosity tends not to be obtained. The kneading temperature is preferably such that the discharge temperature is 160 ° C. or lower, more preferably 150 ° C. or lower. When the discharge temperature exceeds 160 ° C., scorch occurs during kneading and there is a tendency that a good rubber fabric cannot be obtained.

  The kneading time in the first kneading step is preferably 1.5 to 2.0 minutes. When the kneading time is less than 1.5 minutes, there is a tendency that good dispersion cannot be obtained. When the kneading time exceeds 2.0 minutes, the scorch advances too much and a good rubber fabric tends not to be obtained.

  In the first kneading step, in addition to the rubber component and zinc oxide, a tire rubber composition such as a reinforcing agent such as carbon black, silica or calcium carbonate, stearic acid, process oil, anti-aging agent, tackifier, etc. The raw material generally used for the thing can be mix | blended.

  In the second kneading step, all of the remaining zinc oxide is kneaded.

  The kneading temperature in the second kneading step is preferably 90 to 110 ° C. If the kneading temperature is less than 90 ° C, good dispersion of the vulcanizing agent cannot be obtained, and there is a tendency that vulcanization homogeneity cannot be obtained. If the temperature exceeds 110 ° C, scorching occurs and a good rubber fabric is obtained. There is no tendency.

  The kneading time in the second kneading step is preferably 2.5 to 4.0 minutes. If the kneading time is less than 2.5 minutes, good dispersion of the vulcanizing agent is not obtained, and there is a tendency that vulcanization homogeneity cannot be obtained. If the mixing time exceeds 4.0 minutes, scorching occurs and good rubber is obtained. There is a tendency that dough is not obtained.

  In the second kneading step, sulfur, a vulcanization accelerator and the like can be blended in addition to the zinc oxide.

  The pneumatic tire of the present invention is manufactured by rolling the rubber composition obtained by the manufacturing method of the present invention into a film and using it as the inner liner of the innermost layer of the pneumatic tire or the cover rubber of the white sidewall. Is done. As a result, even if the rubber gauge of the prepared inner liner or white cover rubber is reduced by 10%, it is possible to secure a rubber gauge equivalent to that produced with the conventional charged gauge using the normal kneading method when finished. Leads to lighter weight. In addition, the carcass cord, which is a problem in the tire manufacturing process, is prevented from jumping out to the inner liner inner surface and the white side wall is exposed, leading to an improvement in yield.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited only to these.

  Hereinafter, materials and test methods used in Examples and Comparative Examples will be described together.

(material)
Natural rubber 1: SIR-20 (from Indonesia)
Natural rubber 2: SIR-10 (Indonesia)
Chlorobutyl rubber: Chlorobutyl 1068 (chlorine content 1.26% by weight) manufactured by Exxon Chemical Co., Ltd.
Polybutadiene rubber: BR150B manufactured by Ube Industries, Ltd.
EPDM: Esprene 502 manufactured by Sumitomo Chemical Co., Ltd.
Carbon Black: Diamond Black GPF manufactured by Mitsubishi Chemical Corporation
Calcium carbonate: HTO # 12 manufactured by Hitachi Marble Co., Ltd.
Process oil 1: X140 made by Japan Energy Co., Ltd.
Process oil 2: PA32 made by Japan Energy Co., Ltd.
Anti-aging agent: NOCRACK 224 manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Stearic acid: Tsubaki zinc stearate manufactured by Nippon Oil & Fats Co., Ltd .: Ginseng R manufactured by Toho Zinc Co., Ltd.
Powder sulfur: HK200-5 (5% oil treatment) manufactured by Hosoi Chemical Co., Ltd.
Vulcanization accelerator: Noxeller DM manufactured by Ouchi Shinsei Chemical Co., Ltd.

(Test method)
<Adhesiveness (co-curability)>
It was bonded to a rubberized cloth for a tire carcass, and after the press vulcanization, a peel test was carried out with an instrument rubber tester.

<Viscosity (degree of progress of vulcanization)>
Measurement was performed at 130 ° C. using a Mooney tester manufactured by Shimadzu Corporation.

<Air retention>
It was measured according to JIS K7126.

<Dispersibility>
Regarding the vulcanization speed, the variation was measured with a curast meter manufactured by JSR Corporation.

  For carbon black, slices were prepared using a frozen cutting microtome, and the ratio of undispersed carbon black was calculated using a microscope.

<Rolled rubber gauge>
Measured with a dial gauge manufactured by Peacock.

<Finished tire carcass cord lower gauge and finished tire cover rubber gauge>
A section was taken from the shoulder of the tire after vulcanization, and a rubber gauge was measured with a universal projector.

Examples 1-3 and Comparative Examples 1-4 <Rubber Composition for Inner Liner>
The rubber composition was kneaded according to the blending composition and kneading method shown in Table 1. In the first kneading step, the mixture was kneaded for 2.0 minutes using a Banbury mixer and discharged at the temperature shown in Table 1. Next, in the second kneading step, the mixture was kneaded at 100 ° C. for 3.5 minutes using a Banbury mixer. The obtained blend was rolled to produce a rubber sheet. With respect to the obtained rubber sheet, the above-described measurements were performed for adhesiveness, viscosity, air retention and dispersibility. The results are shown in Table 1.

  The rubber sheet of Comparative Example 2 having a high content of chlorobutyl rubber was poor in co-curability with a vulcanized tire, and a good yield could not be obtained. In Comparative Example 3 where the discharge temperature was low, carbon black and other chemicals could not be dispersed well. In Comparative Example 4 having a high discharge temperature, vulcanization progressed excessively during kneading and a good rubber sheet could not be obtained.

Examples 4 to 5 and Comparative Examples 5 to 6 <Pneumatic tire>
225 / 55R17 tires were produced using the blends obtained in Example 1 and Comparative Example 1 as inner liners, and the inner liner rubber gauges of the product tires were compared. In addition, Examples 4 and 5 and Comparative Examples 5 and 6 differ in the point of the charging gauge of the inner liner rubber used for tire molding. The vulcanization conditions of the tire were 1.4 MPa and 183 ° C. for 9 minutes. The results are shown in Table 2.

Examples 6 to 8 and Comparative Examples 7 to 10 <Rubber composition for white cover rubber>
The rubber composition was kneaded according to the blending composition and kneading method shown in Table 3. In the first kneading step, the mixture was kneaded for 2.0 minutes using a Banbury mixer and discharged at the temperature shown in Table 3. Next, in the second kneading step, the mixture was kneaded at 100 ° C. for 3.5 minutes using a Banbury mixer. The obtained blend was rolled to produce a rubber sheet. With respect to the obtained rubber sheet, the above-described measurements were performed for adhesiveness, viscosity, and dispersibility. The results are shown in Table 3.

  In Comparative Example 8 having a low chlorobutyl rubber content, a sufficient increase in viscosity could not be obtained. In Comparative Example 9 having a low discharge temperature, carbon black and other chemicals could not be dispersed well. In Comparative Example 10 having a high discharge temperature, vulcanization progressed excessively during kneading and a good rubber sheet could not be obtained.

Examples 9 to 10 and Comparative Examples 11 to 12
Using the blends obtained in Example 8 and Comparative Example 5 as the white cover rubber, tires of 225 / 55R17 were produced, and the white tire rubber gauges of the product tires were compared. Examples 13 and 14 and Comparative Examples 7 and 8 have different conditions in terms of the gauge of the white cover rubber charged in the tire. The vulcanization conditions of the tire were 1.4 MPa and 183 ° C. for 9 minutes. The results are shown in Table 4.

Claims (4)

Zinc oxide is divided and kneaded into a rubber component containing 35 to 85% by weight of a halogenated butyl rubber and / or a halogenated copolymer of isobutylene and p-methylstyrene. In the manufacturing method,
The rubber composition comprises a rubber component and zinc oxide having a compounding amount of 2 to 8 parts by weight with respect to 100 parts by weight of the rubber component;
The method for producing a rubber composition according to claim 1, wherein in the first kneading step, 10 to 55% by weight of the total zinc oxide is kneaded and discharged at 130 to 160 ° C. A rubber composition obtained by the production method according to claim 1. A pneumatic tire having an inner liner made of the rubber composition according to claim 2. A pneumatic tire having a white side wall cover rubber made of the rubber composition according to claim 2.